4 General

03.663GPPStage 2Support of GSM Mobile Number Portability (MNP)TS

4.1 Overview

Mobile Number Portability (MNP) is the ability for a mobile subscriber to change the GSM subscription network within a portability domain whilst retaining her original MSISDN or MSISDNs.

As part of the porting process administrative actions have to be performed by the GSM network operators of the number range holder network, donor network, recipient network and, as an option, by operators of other national GSM networks as follows:

a) if the number range holder network is identical with the donor network:

Recipient network:

add an entry in the HLR;
add an entry in the Number Portability Database.

Donor network:

add an entry in the Number Portability Database;
delete the entry related to the ported MSISDNs in the HLR.

Other networks in the portability domain:

add an entry in the Number Portability Database (if direct routeing is used).

b) if the number range owner network is identical with the recipient network:

Recipient network:

add an entry in the HLR;
delete any entry related to the ported MSISDN in the Number Portability Database.

Donor network:

delete any entry related to the ported MSISDN in the Number Portability Database;
delete the entry related to the ported MSISDNs in the HLR.

Other networks in the portability domain:

delete any entry related to the ported MSISDN in the Number Portability Database.

c) if the number range holder network is different from both the recipient and the donor network:

Recipient network:

add an entry in the HLR;
add an entry in the Number Portability Database.

Number range holder network:

update the Number Portability Database

Donor network:

delete (or update) the entry in the Number Portability Database;
delete the entry related to the ported MSISDNs in the HLR.

Other networks in the portability domain:

update the Number Portability Database (if an entry for the ported MSISDN exists ).

Note that the order of sequence for the administrative actions to be performed both within a network and by different network operators is significant with respect to prevention of disruption in service to the mobile subscriber and prevention of looping calls between networks during the porting process.

Termination of a subscription for a ported number results in the deletion of any entry in an HLR and NPDB of that number.

If a call fails because databases are not correctly synchronised, the network entity which detects the inconsistency will raise an MNP specific alarm to the operation and maintenance subsystem.

The present document does not specify the porting process; it specifies the functionality needed to set-up calls to both ported and non ported subscribers (normative annex A and normative annex C) and the functionality needed to relay non-call related signalling messages to the HLR in the subscription network (normative annex B).

4.2 Compatibility

The IAM sent to the subscription network may contain additional routeing information. Within a portability domain the method how to convey the Routeing Number in the IAM between 2 PLMNs shall be agreed upon by the 2 network operators involved (see also [7]).

In general, IN-based and MNP-SRF (call-related) solutions are compatible and may coexist in the same portability domain. The only restriction refers to the case where the number range holder network relays call-related MAP messages (i.e. SRI for national calls) to the subscription network. If this solution is selected by at least one network operator within a portability domain, all the PLMNs and transit networks affected must fulfil the following requirements:

1. The SCCP interfaces between networks in a portability domain must be agreed. This refers to the SCCP addressing mechanism being used (e.g. number lengths, natures of address and translation types for call-related MAP messages).
For messages which do not cross network boundaries the SCCP addressing mechanism is a choice of the network operator.

2. The subscription network must be able to generate the SRI ack to allow the onward routeing of the call from the number range holder network to the subscription network.

In the rest of the possible architectures for MNP, no interworking problems have been identified. In these cases, network architectures used within one PLMN (e.g. IN, MNP-SRF) are regarded as operator dependent.

In order to avoid loops and incompatibility situations, all the networks within a portability domain shall use the same routeing convention either direct routeing, indirect routeing or indirect routeing with reference to the Subscription network. As an alternative, indirect routeing can interwork successfully with direct routeing if the routeing number is transferred in the IAM or if dedicated traffic connections are used.

4.3 Common Functionality of the MNP-SRF

In a PLMN which supports mobile number portability, SCCP messages sent to an HLR may be relayed by an MNP-SRF. Depending on the implemented solution (IN-based or MNP-SRF-based), on the type of message (call-related or non-call-related) and on the porting status of the called subscriber the MNP-SRF may modify the SCCP called party address and route the message to a different HLR or to the subscription network, or terminate the dialogue and response to the INE.

Figure 1 shows the general steering functionality for SCCP message routeing. It shows the SCCP routeing principle for mobile number portability within a network.

Note that call related messages in the IN-based solution are not routed to the MNP-SRF. Therefore Normative Annex A of the present document does not mention the MNP-SRF.

However, the usage of the IN-based solution for the call-related messages should allow operators to have the routeing of the non call-related messages determined in the same database.

In order to guard against the possibility that the porting data for an MSISDN is inconsistent between PLMNs in a porting domain, the SCCP hop counter may be used to prevent indefinite looping of messages between PLMNs. The MNP-SRF would then decrement the SCCP hop counter for every message that is relayed. It should be noted that the use of the SCCP hop counter requires the use of unsegmented SCCP XUDT messages as defined in ITU-T 1996 SCCP recommendations.

Figure 1: Steering Function for SCCP Message routeing

Figure 2 shows the process MNP_SRF in the MNP-SRF. The procedures MNP_SRF_MATF_Call_Related and MNP_SRF_Non_Call_Related are described in Normative Annex C and Normative Annex B of the present document. Note that in networks which support the IN-based solution for call related signalling, a distinction on SCCP level for call related and non-call related messages is needed and that the MNP-SRF does not require to include a MATF since call related messages are not routed to the MNP-SRF.

The test "call-related" is a test on the SCCP Translation Type if a dedicated Translation Type value for call related messages is used in the network. The handling of SCCP messages in the MNP-SRF in networks which do not make use of a dedicated Translation Type value for call related messages is for further study.

Figure 2: Process MNP_SRF